The present invention relates to an electronic watch having electronic circuits such as an oscillator circuit, a frequency dividing circuit, and a drive circuit, and which is driven by an internal battery power supply.
At present, electronic watches having a power supply and an electronic circuit, and particularly those using a quartz oscillator circuit as a reference time base, are in wide use. FIG. 4 shows examples of electronic watches, (a) showing an analog watch, in which the time is indicated by an hour hand 1, a minute hand 2, and a second hand 3, and (b) showing a digital watch, in which the hour, minute, second, and calendar are indicated digitally by numerals.
The user pulls out a stem 4 of the watch as shown by 4a, and turns the stem so as to set the hands to start using the watch. If time indication becomes skewed after a long period of use, the user must operate the stem 4 to correct the hand positions.
In a general electronic watch, as a convenience in setting the hands, a switch linked to the stem operates when the stem is pulled out to the position 4a so as to immediately stop the movement of the hands.
Therefore, the usual procedure for setting the hands is to pull out the stem 4 when the second hand points to 12 o""clock, so as to stop the movement of the hands, and if necessary to rotate the stem in accordance with a time signal from the radio or TV, after which the stem 4 is pushed in to start the movement of the hands. By doing this, even the second hand can be accurately set.
The configuration of an electronic watch such as this is shown in the block diagram of FIG. 5, in which 5 is an oscillator circuit, this generally being a quartz oscillator circuit using a quart oscillating element 6. The oscillator output passes through two stages or a first frequency dividing circuit 7 and a second frequency dividing circuit 8, and is divided thereby down to 1 Hz, which is suitable for driving the second hand.
The frequency-divided output passes through a waveshaping circuit 9 and is applied to a drive circuit 10, the coil of a motor 11 being thereby excited so as to move the hands 12. Although not shown in the drawing, the motor 11 and the hands 12 are linked by a gear train.
A voltage regulator circuit 13 is provided as a power supply circuit, this being connected to power supply voltages VDD and VSS from a battery, and generating a voltage Vreg, which is lower than the battery voltage.
As shown in the drawing, the oscillator circuit 5 and the first frequency dividing circuit 7 are driven by the output voltage Vreg of the voltage regulator circuit 13, and the second frequency dividing circuit 8 and subsequent circuitry are driven not by Vreg, but rather by a battery voltage.
The reason for driving the oscillator circuit 5 and the first frequency dividing circuit 7 by a specially provided voltage regulator circuit 13 is, because these parts deal with high-frequency signals, to reduce the drive voltage and the power consumption, and also operate the oscillator circuit that determines the accuracy of the watch with good stability, from the output voltage Vref of the voltage regulator circuit 13 that does not vary, even if the battery voltage drops.
The switch SW is constructed so that it operates in concert with the stem 4 shown in FIG. 4. That is, in the condition in which the watch is in use, with the stem 4 pushed in, a switching piece 14 shown in FIG. 5 is moved away from the ON contact 15. The switching piece 14 is connected to the power supply voltage VDD, and the ON contact 15 is connected, via an n-channel transistor Tr1, to the power supply voltage VSS.
The transistor Tr1, being connected to VDD, is always in the conducting state. The transistor Tr1 is a pull-down resistance, which pulls down the potential of the ON contact 15 to VSS. The ON contact 15 is connected to the reset terminal R of the frequency dividing circuit 8, and because this is at a low potential, the second frequency dividing circuit 8 is not reset, and continues to operate.
When the user pulls out the stem to 4a as shown in FIG. 4 in order to set the hands, the switching piece 14 of FIG. 5, linked to the stem 4, makes connection with the ON contact 15. When this occurs, the ON contact 15 potential rises from VSS to VDD, so that a valid signal is applied to the reset terminal R of the second frequency dividing circuit 8, thereby stopping the output of the signal from the second frequency dividing circuit 8, so that the motor 11 is no longer driven, thereby stopping the hands 12.
In this condition, when the user sets the hands and pushes in the stem, the switching piece 14 moves away from the ON contact 15, so that the potential on the ON contact, this being the voltage applied to the reset terminal R of the second frequency dividing circuit 8, decreases to VSS, and because the oscillator circuit 5 and first frequency dividing circuit 7 were still in the driven condition, the second frequency dividing circuit 8 reset condition is released, so that it immediately starts again to output a signal, thereby driving the motor 11 and starting the movement of the hands 12.
In this manner, the stoppage of the hands when the stem is pulled out is convenient in setting the hands, and because the motor is not driven, it is possible to greatly reduce the power consumption. Because of this, it possible to prevent wearing down of the battery before a watch is delivered to a user.
For this reason, during the period in the factory, or in a warehouse, or when the watch is being displayed in a shop, the stem is pulled out to stop the hands.
If the stem is pulled out to stop the hands, it is possible to reduce the wear down of the battery because of the reduction in current consumption, although in this condition there is still current consumed by the oscillator circuit and the first frequency dividing circuit. For this reason, in a case, for example, in which a long time elapses before the users receives the watch, there can be a non-negligible depletion of battery.
One approach to achieving a further power savings that can be envisioned is that of not only stopping the hands when the stem is pulled out, but also stopping the oscillator circuit and the first frequency dividing circuit as well, although this approach is not applicable so simply.
The resonant element used in the oscillator circuit is normally a quartz resonant element with a characteristic frequency of approximately 32 kHz, and once the oscillation thereof is stopped, some time is required when restarting the oscillation for the oscillator to build up and become normal. Because of this, when the stem is pushed in, time is required before the circuit operates normally, so that after the stem is pushed in the hands do not move normally one second thereafter, thereby preventing the proper setting of the hands.
The inventors of the present invention, in a previous Japanese Patent Application No. 52-46453 (Japanese Examined Patent Publication (KOKOKU)No. 61-37585) proposed a quartz watch in which, when the stem is pulled out, not only the hands, but also the oscillation is stopped.
In this watch, the number of seconds required for the previously stopped quartz resonant element to reach a sufficient amplitude is priorly predicted, and when the stem is pushed in a drive pulse is first generated for that number of seconds, so as to advance the hands. By doing this, in addition to achieving a power savings greater than in the past when the stem is pulled out, after the stem is pushed in, there is no delay in the time display.
However, while the disclosure of the Japanese Patent Application No. 52-46453 (Japanese Examined Patent Publication (KOKOKU)No. 61-37585) compensates for the. delay in operation startup after setting of the time, it is difficult to adjust the compensation value to the actual delay time, and troublesome processing is required, for example, to select a compensation value appropriate to the quartz resonant element characteristics and the circuit specifications.
In the above-noted electronic watch, it is necessary not only to save power in the case of setting the hands or when the watch is stored for a long period of time, but it is also necessary in the case in which the output voltage of a power supply used in the electronic watch, this being a primary cell, a secondary cell or an electrical generator and a secondary cell falls below a prescribed voltage value, to reduce the decrease in battery capacity, because of the desire to save power used by the electronic watch, and in particular to shorten the amount of time required to charge a secondary cell.
Accordingly, it is an object of the present invention to provide an electronic watch that solves the problems of the prior art, and normally enables hand setting, wherein during storage or when the power supply voltage has dropped below a pre-established reference value, achieves a great power savings, and a method for operating an electronic watch.
In the present invention, in order to achieve the above-noted object, the basic technical constitution adopted is as follows.
Specifically, a first aspect of the present invention is a power-saving electronic watch having a power supply, an oscillator circuit, a frequency dividing circuit, and a drive circuit, this electronic watch further having an externally operable switch and a counting circuit that counts a prescribed time, wherein after the switch goes into the ON condition, and after a prescribed time elapses, minimally the oscillator circuit is stopped.
A second aspect of the present invention is a power-saving electronic watch having a power supply, an oscillator circuit, a frequency dividing circuit, and a drive circuit, this electronic watch further having voltage detection circuit that detects a drop in power supply voltage, wherein an output signal of the voltage detection circuit minimally stops the oscillator circuit.
A third aspect of the present invention is a method for operating an electronic watch having a power supply, an oscillator circuit, a frequency dividing circuit, and a drive circuit, this electronic watch further having an externally operable switch and a counting circuit that counts a prescribed time, wherein after the switch goes into the ON condition, after a prescribed time elapses, minimally the oscillator circuit is stopped, and a method for operating an electronic watch having a power supply, an oscillator circuit, a frequency dividing circuit, and a drive circuit, this electronic watch further having voltage detection circuit that detects a drop in power supply voltage, whereby, in response to detection and output of a signal therefrom, the oscillator circuit is minimally stops the oscillator circuit.